Characterization of Crystalline Defects Using CBED Techniques

1990 ◽  
Vol 48 (2) ◽  
pp. 520-521
Author(s):  
R. Pérez
Keyword(s):  
Fourier Coefficients ◽  
Stacking Faults ◽  
Small Region ◽  
Dynamical Theory ◽  
Convergent Beam Electron Diffraction ◽  
Zero Order ◽  
Image Contrast ◽  
Convergent Beam ◽  
Theoretical Simulations

Convergent beam electron diffraction (CBED) is a technique widely used for obtaining crystallographic information from a small region in a specimen. In recent years CBED technique have been mainly used for the symmetry characterization of perfect crystals. However, the study of crystals containing defects by CBED have received little attention in the literature1-4. The results presented in this communication explore some of the image contrast characteristics obtained in theoretical simulations of zero-order laue zone (ZOLZ) reflections. These calculations have been carried out for crystalline specimens wich contain dislocations or stacking faults. The theoretical simulations are based on the multibeam form of the dynamical theory using ato mic scattering factors reported by Doyle and Turner5. The Fourier coefficients of the lattice pottential were Debye-Waller corrected in all cases. Some of the most important parameters which have strong influence on image contrast have been explored. These include, the thickness of the specimen, the depth of defect in the specimen, the multibeam effects, the nature of the defects etc.

Strain measurement in In0.2Ga0.8As/GaAs quantum wires by convergent beam electron diffraction

1995 ◽  
Vol 53 ◽  
pp. 444-445
Author(s):  
S. Hillyard ◽  
Y.-P. Chen ◽  
J.D. Reed ◽  
W.J. Schaff ◽  
L.F. Eastman ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Semiconductor Lasers ◽  
Quantum Wire ◽  
Quantum Wires ◽  
Convergent Beam Electron Diffraction ◽  
Zero Order ◽  
Beam Electron ◽  
Local Lattice ◽  
Device Applications ◽  
Convergent Beam

The positions of high-order Laue zone (HOLZ) lines in the zero order disc of convergent beam electron diffraction (CBED) patterns are extremely sensitive to local lattice parameters. With proper care, these can be measured to a level of one part in 104 in nanometer sized areas. Recent upgrades to the Cornell UHV STEM have made energy filtered CBED possible with a slow scan CCD, and this technique has been applied to the measurement of strain in In0.2Ga0.8 As wires.Semiconductor quantum wire structures have attracted much interest for potential device applications. For example, semiconductor lasers with quantum wires should exhibit an improvement in performance over quantum well counterparts. Strained quantum wires are expected to have even better performance. However, not much is known about the true behavior of strain in actual structures, a parameter critical to their performance.

Anomalous electron absorption effects in metal foils: theory and comparison with experiment

1962 ◽  
Vol 269 (1336) ◽  
pp. 80-103 ◽  
Keyword(s):  
Fourier Coefficients ◽  
Stacking Faults ◽  
Formal Theory ◽  
Dynamical Theory ◽  
Anomalous Absorption ◽  
Physical Explanation ◽  
Absorption Effect ◽  
Metal Foils ◽  
Comparison With Experiment ◽  
Transmission Electron

The two-beam dynamical theory of electron diffraction in absorbing crystals has been applied to explain features of bend and thickness extinction contours and of images of stacking faults observed on transmission electron micrographs of metal foils. Inelastic scattering processes affect the intensities of the elastically scattered waves and give rise to 4 anomalous ’ transmission (Borrmann) effects. The formal theory takes account of these effects phenomenologically by the use of a complex lattice potential but ignores the contribution of the inelastically scattered electrons to the image. In the theory absorption is described by certain parameters ξ' 0 and ξ' g with dimensions of length. These parameters are determined by Fourier coefficients of the imaginary part of the potential in the same manner as the extinction distance ξ g is determined by the Fourier coefficient of the real part. A simple physical explanation of the ‘anomalous’ absorption effect is developed in terms of the two crystal wave fields. This explanation is particularly helpful in understanding details of bend and thickness contours and of images of stacking faults. The theory is at present phenomenological because the detailed mechanism of the absorption process is not understood. Nevertheless, comparison of the theory with observations enables the absorption parameters to be roughly estimated.

Characterization of Contacting Boundaries between Nanoparticles with LACBED

2003 ◽  
Vol 9 (3) ◽  
pp. 237-244 ◽  
Author(s):  
Yiming Yao ◽  
Anders R. Thölén
Keyword(s):  
Nanocrystalline Materials ◽  
Large Angle ◽  
Convergent Beam Electron Diffraction ◽  
Average Accuracy ◽  
Accuracy Of Measurements ◽  
Wide Range ◽  
Grain Orientations ◽  
Rotation Parameters ◽  
Convergent Beam

The boundary parameters between contacting spherical bcc-Fe particles have been characterized with the Large Angle Convergent Beam Electron Diffraction (LACBED) technique. The average accuracy of measurements can reach 0.07°. The rotation parameters are interpreted using matrix algebra and evaluated according to the CSL model. The deviation between the experimental results and the reference misorientations given in the CSL model is determined. It is possible to reveal preferential misorientations between irregularly shaped particles with a size less than 100 nm. The method can be applied to nanoparticles and nanocrystalline materials with a wide range of grain orientations, and it is possible to modify it into an automatic method for TEM measurements.

The characterization of an SCS6/Ti–6Al–4V MMC interphase

1989 ◽  
Vol 4 (2) ◽  
pp. 327-335 ◽  
Author(s):  
C. Jones ◽  
C. J. Kiely ◽  
S. S. Wang
Keyword(s):  
Metal Matrix ◽  
Chemical Interaction ◽  
Auger Spectroscopy ◽  
Carbon Layer ◽  
Convergent Beam Electron Diffraction ◽  
Interphase Region ◽  
The Matrix ◽  
Convergent Beam

Using TEM, Auger spectroscopy, EDX, and convergent beam electron diffraction, a thorough characterization of the interphase region between SCS6 fibers and Ti–6Al–4V matrix in a metal matrix composite has been performed. The interphase region is shown to be very complex, consisting of numerous layers of varying compositions and thicknesses. The chemical interaction of the fiber and matrix results in a 0.5–1.5 μm thick TiC layer. Evidence for the existence of a Tix Siy (C) layer is also presented. The SCS6 overlayer on the fibers has inhibited any chemical interaction between the matrix and the SiC filament itself, 60% of the interphase region originating from the SCS6 protective coating. In situ fracture experiments (in an Auger spectrometer) reveal that fracture takes place between the TiC and an amorphous carbon layer.

Preparation and Characterization of Single-crystal Aluminum Nitride Substrates

1999 ◽  
Vol 595 ◽  
Author(s):  
Leo J. Schowalter ◽  
J. Carlos Rojo ◽  
Nikolai Yakolev ◽  
Yuriy Shusterman ◽  
Katherine Dovidenko ◽  
...  
Keyword(s):  
Aluminum Nitride ◽  
Single Crystal ◽  
Convergent Beam Electron Diffraction ◽  
Large Single Crystal ◽  
High Quality ◽  
Afm Imaging ◽  
Convergent Beam ◽  
Edge Dislocations ◽  
Etching Effect

AbstractLarge (up to 10mm diameter) aluminum nitride (AlN) boules have been grown by the sublimation-recondensation method to study the preparation of high-quality single crystal substrates. The growth mechanism of the boules has been studied using AFM. It has been determined that large single crystal grains in those boules grow with a density of screw dislocations below 5×104 cm−3 while edge dislocations are at lower density (none were observed). High-quality AlN single crystal substrates for epitaxial growth have been prepared and characterized using Chemical Mechanical Polishing (CMP) and AFM imaging, respectively. Also, the differential etching effect of KOH solutions on the N and Al-terminated faces of AlN on vicinal c-faces has been investigated. In order to identify the N or Al-terminated face, convergent beam electron diffraction has been used.

CBED Tools for semi-automatic measurement of crystal thicknesses

2017 ◽  
Vol 50 (1) ◽  
pp. 313-319 ◽  
Author(s):  
Shi Honglong ◽  
Luo Minting ◽  
Wang Wenzhong
Keyword(s):  
Automatic Measurement ◽  
Convergent Beam Electron Diffraction ◽  
Zero Order ◽  
Crystal Thickness ◽  
Beam Electron ◽  
Linear Fitting ◽  
Fitting Method ◽  
Kikuchi Lines ◽  
Convergent Beam ◽  
Thin Crystal

Convergent-beam electron diffraction (CBED) is one of the most popular techniques to measure crystal thickness. The traditional measurement involves linear fitting of several fringes across the CBED disc, but for a thin crystal with fewer than three fringes the usefulness of this method will be limited. CBED Tools, a free plugin for the DigitalMicrograph software, provides a fast (∼1–2 min) and accurate algorithm to measure the crystal thickness on the basis of the linear fitting method, but it is also capable of determining the crystal thickness when it is very thin and only one fringe or part of the first fringe is recorded. CBED Tools can also be utilized to handle the severely distorted CBED pattern obtained when the zero-order Laue zone Kikuchi lines overlap with the fringes.

scholarly journals Structural Defects in Laterally Overgrown GaN Layers Grown on Non-polar Substrates

2006 ◽  
Vol 955 ◽  
Author(s):  
Zuzanna Liliental-Weber ◽  
X. Ni ◽  
H. Morkoc
Keyword(s):  
Large Angle ◽  
Stacking Faults ◽  
Growth Direction ◽  
Convergent Beam Electron Diffraction ◽  
Structural Defects ◽  
Threading Dislocations ◽  
Beam Electron ◽  
Transmission Electron ◽  
Wing Width ◽  
Convergent Beam

ABSTRACTTransmission electron microscopy was used to study defects in lateral epitaxial layers of GaN which were overgrown on a template of a-plane (1120) GaN grown on (1102) r-plane Al2O3. A high density of basal stacking faults is formed in these layers because the c-planes of wurtzite structure are arranged along the growth direction. Density of these faults is decreasing at least by two orders of magnitude lower in the wings compared to the seed areas. Prismatic stacking faults and threading dislocations are also observed, but their densities drastically decrease in the wings. The wings grow with opposite polarities and the Ga-wing width is at least 6 times larger than N-wing and coalescence is rather difficult. Some tilt and twist was detected using Large Angle Convergent Beam Electron Diffraction.

Characterization Of APB's In GaP

1996 ◽  
Vol 442 ◽  
Author(s):  
Dov Cohen ◽  
C. Barry Carter
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Diffraction ◽  
Convergent Beam Electron Diffraction ◽  
Antiphase Boundaries ◽  
Beam Electron ◽  
Transmission Electron ◽  
Convergent Beam ◽  
Crystallographic Orientations

AbstractAntiphase boundaries in GaP crystals epitactically grown on Si (001) have been characterized using transmission electron microscopy. Convergent-beam electron diffraction was used to identify the antiphase-related grains. The antiphase boundaries were observed to adopt facets parallel to specific crystallographic orientations. Furthermore, stacking-fault-like contrast was observed along the interface suggesting that the domains may be offset from one another by a rigid-body lattice translation.

Dislocations in YBa2Cu3O7−δ (δ = 0.77)

1990 ◽  
Vol 48 (4) ◽  
pp. 72-73
Author(s):  
Yimei Zhu ◽  
Hong Zhang ◽  
A.R. Moodenbaugh ◽  
M. Suenaga
Keyword(s):  
Electron Microscope ◽  
Electron Diffraction ◽  
Displacement Vector ◽  
Stacking Faults ◽  
Spot Size ◽  
Convergent Beam Electron Diffraction ◽  
Burgers Vector ◽  
Beam Electron ◽  
X Ray ◽  
Convergent Beam

Abundant dislocations and dislocations associated with stacking faults were observed and characterized in YBa2Cu3O7−δ (δ= 0.77). The crystallographic orientation of the dislocation and the fault were analyzed using Kikuchi patterns matched with computer generated Kikuchi maps. The Burgers vector of the dislocation and the displacement vector of the fault were determined by using the g·b = 0 and g · R=0 criteria.Bulk samples of YBa2Cu3O7 were produced by standard pressing and sintering up to 970 °C. Samples were heated in air, then quenched into liquid nitrogen to reduce oxygen content. Subsequent anneal at 200 ° C took place with samples sealed in silica with 1/2 atm. of argon. TEM specimens were thinned by ion mill and examined in a JEOL 2000FX electron microscope operating at 200kv.X-ray powder diffraction and convergent beam electron diffraction with 200 Å spot size show that YBa2Cu3O6.23 has a tetragonal structure.

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